(1) Field of the Invention
This invention relates to a resin-sandwiched metal laminate for use in, for example, automobiles, domestic electric appliances and building materials, etc., a process and apparatus for producing the same and a process for producing a resin film for the resin-sandwiched metal laminate.
(2) Prior Art
Generally, a resin-sandwiched metal laminate is produced by applying a resin to one side of one metal sheet or band, placing another metal sheet or band on the resin-applied side and press-bonding the sheets or bands, or by placing a resin film between two metal sheets or bands, and likewise press-bonding the sheets or bands,[Japanese Patent Application Kokai (Laid-open) No. 62-53833, etc.].
It is also known to add an electroconductive filler such as fibers, powders and other irregularly shaped particles of metals, for example, iron, nickel, carbon steel, stainless steel, aluminum, titanium, etc., and non-metals, for example, carbon, etc. to the resin layer in the resin-sandwiched metal laminate, thereby endowing the resin-sandwiched metal laminate with an electroconductivity to obtain a weldability [Japanese Patent Application Kokai (Laid-open) No. 59-145142, etc.]. The electroconductive filler is provided throughout the resin layer between the two metal sheets and thus the resin-sandwiched metal laminate has a good weldability in any region on the face and back sides of the resin-sandwiched metal laminate.
In the production of a vessel-shaped member, etc., for example, as shown in FIG. 17, a drum body 40 is formed, and flanges 41 are made of the upper and lower ends 41 of the drum body 40 to weld the flanges 41 to another member 43. In that case, and electroconductive filler-containing resin can be provided in the regions at both side edges of a resin-sandwiched metal laminate and an electroconductive filler-free resin can be provided in the center region between the side edge regions. That is, it is not advantageous to provide the electroconductive filler-containing resin in the regions not destined for the welding, because the adhesiveness of the resin to the metal and the vibration damping of the resin are a little inferior to those of the electroconductive filler-free resin. Furthermore, the electroconductive filler is used wastefully in that case. And particularly in the case of an expensive filler such as nickel, etc., such disadvantages as considerably high production cost, etc. are inevitably entailed.
In the production of the resin-sandwiched metal laminate, a portion of the resin is squeezed out of both edges of the metal sheets or bands during the press-bonding, and remains attached to the surfaces of the metal sheets or bands to deteriorate the quality of the laminate, etc. That is, as shown in FIG. 15, when a resin 2 is provided between metal sheets or bands 10 and 10a and press-bonded by rolls 35 and 25a in the conventional process, a portion 2' of the resin 2 is squeezed out at the edges and is attached to the surfaces of the metal sheets or bands 10 and 10a, because both edges of the metal sheets or bands 10 and 10a take a straight form and thus the resin is squeezed out at the edges of the metal sheets or bands during the press-bonding.
It is also known to provide a resin between metal bands and press-bond the resin between the metal sheets throughout the full width in the width direction of the metal bands by pressing rolls [Japanese Patent Application Kokai (Laid-open) No. 50-27750].
However, in the production of such metal laminate, the pressing force is lighter in the regions at both side edges in the width direction of metal bands than in the center region, and this phenomenon is remarkable particularly in the case of using mill edge metal sheets. As shown in FIG. 16, when a resin 2 provided between metal bands 10 and 10a is press-bonded under a pressing force by press rolls 25 and 25a, which press the metal bands throughout the full width in the width direction of the metal bands, the resin 2 at the edge drop parts (whose one end is shown in the drawing) at both side edges in the width direction of the metal bands is not securely press-bonded between the metal bands 10 and 10a. Thus, such disadvantages as considerable deterioration of laminate quality, etc. are inevitably entailed.